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Learn how to – Deploy Lightweight Kubernetes Cluster in 5 minutes with K3s

How to Kubernetes Linux Tutorials May 8, 2023

Learn how to – Deploy Lightweight Kubernetes Cluster in 5 minutes with K3s.

You want to deploy a Lightweight Kubernetes Cluster with ease and less memory footprint?, all in a binary less than 40mb?. Kubernetes has been a game changer in how containerized workloads are deployed and managed at immense scale. The main challenge for Developers revolve around setup process and resource requirements to have a working Kubernetes Cluster.

For Production deployment refer to:

For semi manual deployment with Kubeadm, check:

For Development and test impetus, a user should be able to deploy Kubernetes with least resource utilization and low hardware specs. K3s is a tiny Kubernetes distribution created and optimized by Rancher team to run on IoT and ARM powered devices.

Since K3s is optimized to use less resources, some Kubernetes features are stripped off. These include:

  • Legacy, alpha, non-default features
  • Most in-tree plugins (cloud providers and storage plugins) which can be replaced with out of tree addons.
  • etcd3 replaced by sqlite3 as the default storage mechanism

Deploy Lightweight Kubernetes Cluster in 5 minutes with K3s

For my deployment, I have three servers running Debian 10 each with 1GB of Ram and 1vcpu. One of the servers will be used as master and other two as worker nodes.

$ openstack server list
+--------------------------------------+-------------------+---------+-----------------------------------+-----------+-----------+
| ID                                   | Name              | Status  | Networks                          | Image     | Flavor    |
+--------------------------------------+-------------------+---------+-----------------------------------+-----------+-----------+
| 4df6a6dc-26e8-4ae0-8b6e-2f97daec0ef3 | k3s-master        | ACTIVE  | private=10.10.1.159               | Debian-10 | m1.tiny   |
| 5ca13239-b745-4f62-ab11-0a27949c9b35 | k3s-node02        | ACTIVE  | private=10.10.1.142               | Debian-10 | m1.tiny   |
| a54997f2-4d94-4718-86ab-73609b328761 | k3s-node01        | ACTIVE  | private=10.10.1.126               | Debian-10 | m1.tiny   |
+--------------------------------------+-------------------+---------+-----------------------------------+-----------+-----------+

I’ll add A records for the servers on /etc/hosts file on each server.

$ sudo vim /etc/hosts
10.10.1.159 k3s-master
10.10.1.126 k3s-node01
10.10.1.142 k3s-node02

Install K3s on Master node

There are many ways to run k3s. The quickest method is installation via provided bash script. This script provides a convenient way for installing to systemd or openrc.

curl -sfL https://get.k3s.io | sh -

Installation output.

[INFO]  Finding release for channel stable
[INFO]  Using v1.25.6+k3s1 as release
[INFO]  Downloading hash https://github.com/k3s-io/k3s/releases/download/v1.25.6+k3s1/sha256sum-amd64.txt
[INFO]  Downloading binary https://github.com/k3s-io/k3s/releases/download/v1.25.6+k3s1/k3s
[INFO]  Verifying binary download
[INFO]  Installing k3s to /usr/local/bin/k3s
[INFO]  Skipping installation of SELinux RPM
[INFO]  Creating /usr/local/bin/kubectl symlink to k3s
[INFO]  Creating /usr/local/bin/crictl symlink to k3s
[INFO]  Creating /usr/local/bin/ctr symlink to k3s
[INFO]  Creating killall script /usr/local/bin/k3s-killall.sh
[INFO]  Creating uninstall script /usr/local/bin/k3s-uninstall.sh
[INFO]  env: Creating environment file /etc/systemd/system/k3s.service.env
[INFO]  systemd: Creating service file /etc/systemd/system/k3s.service
[INFO]  systemd: Enabling k3s unit
Created symlink /etc/systemd/system/multi-user.target.wants/k3s.service → /etc/systemd/system/k3s.service.
[INFO]  systemd: Starting k3s

The service is automatically started after installation.

$ systemctl status k3s
● k3s.service - Lightweight Kubernetes
     Loaded: loaded (/etc/systemd/system/k3s.service; enabled; vendor preset: enabled)
     Active: active (running) since Wed 2023-03-08 11:56:10 UTC; 16s ago
       Docs: https://k3s.io
    Process: 1412 ExecStartPre=/bin/sh -xc ! /usr/bin/systemctl is-enabled --quiet nm-cloud-setup.service (code=exited, status=0/SUCCESS)
    Process: 1414 ExecStartPre=/sbin/modprobe br_netfilter (code=exited, status=0/SUCCESS)
    Process: 1416 ExecStartPre=/sbin/modprobe overlay (code=exited, status=0/SUCCESS)
   Main PID: 1421 (k3s-server)
      Tasks: 56
     Memory: 544.0M
        CPU: 22.008s
     CGroup: /system.slice/k3s.service
             ├─1421 "/usr/local/bin/k3s server"
             └─1466 containerd -c /var/lib/rancher/k3s/agent/etc/containerd/config.toml -a /run/k3s/containerd/containerd.sock --state /run/k3s/containerd --root /var/lib/rancher/k3s/agent/containe>

Mar 08 11:56:24 jammy k3s[1421]: I0308 11:56:24.641228    1421 iptables.go:270] bootstrap done
Mar 08 11:56:25 jammy k3s[1421]: W0308 11:56:25.294598    1421 handler_proxy.go:105] no RequestInfo found in the context
Mar 08 11:56:25 jammy k3s[1421]: W0308 11:56:25.294635    1421 handler_proxy.go:105] no RequestInfo found in the context
Mar 08 11:56:25 jammy k3s[1421]: E0308 11:56:25.295828    1421 controller.go:113] loading OpenAPI spec for "v1beta1.metrics.k8s.io" failed with: Error, could not get list of group versions for APIS>
Mar 08 11:56:25 jammy k3s[1421]: I0308 11:56:25.295900    1421 controller.go:126] OpenAPI AggregationController: action for item v1beta1.metrics.k8s.io: Rate Limited Requeue.
Mar 08 11:56:25 jammy k3s[1421]: E0308 11:56:25.295963    1421 controller.go:116] loading OpenAPI spec for "v1beta1.metrics.k8s.io" failed with: failed to retrieve openAPI spec, http error: Respons>
Mar 08 11:56:25 jammy k3s[1421]: , Header: map[Content-Type:[text/plain; charset=utf-8] X-Content-Type-Options:[nosniff]]
Mar 08 11:56:25 jammy k3s[1421]: I0308 11:56:25.297181    1421 controller.go:129] OpenAPI AggregationController: action for item v1beta1.metrics.k8s.io: Rate Limited Requeue.
Mar 08 11:56:25 jammy k3s[1421]: E0308 11:56:25.771986    1421 dns.go:157] "Nameserver limits exceeded" err="Nameserver limits were exceeded, some nameservers have been omitted, the applied nameser>
Mar 08 11:56:25 jammy k3s[1421]: I0308 11:56:25.922767    1421 request.go:690] Waited for 1.216625763s due to client-side throttling, not priority and fairness, request: POST:https://127.0.0.1:6443>

A kubeconfig file is written to /etc/rancher/k3s/k3s.yaml:

$ sudo cat /etc/rancher/k3s/k3s.yaml
apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: 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
    server: https://127.0.0.1:6443
  name: default
contexts:
- context:
    cluster: default
    user: default
  name: default
current-context: default
kind: Config
preferences: {}
users:
- name: default
  user:
    client-certificate-data: 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
    client-key-data: LS0tLS1CRUdJTiBFQyBQUklWQVRFIEtFWS0tLS0tCk1IY0NBUUVFSUp2MEE5UjUramtDRi82RW9NWXZadU9MYmh3eXlXKzZwcEhQWFpWVXdvNUlvQW9HQ0NxR1NNNDkKQXdFSG9VUURRZ0FFczRKTzc3bkdrWVgyUGFESjRYNjBOdThuUHpyZWltZVFSUVEvOFEwdm5FY29mbGwwRktMYwprYVEvWTdreEJ5cW81N3dZdkF4NHhrYTJoemk5ZzZ1WjdBPT0KLS0tLS1FTkQgRUMgUFJJVkFURSBLRVktLS0tLQo=

Other utilities installed are:

  • kubectl
  • crictl
  • k3s-killall.sh
  • k3s-uninstall.sh

Install K3s on Worker Nodes

To install on worker nodes we should pass K3S_URL along with K3S_TOKEN or K3S_CLUSTER_SECRET environment variables.

The K3S_TOKEN is created at /var/lib/rancher/k3s/server/node-token on first node.

$ sudo cat /var/lib/rancher/k3s/server/node-token
K1037242285167f68f26c05e9221751153591384faab8bb6318c3be56a1ff6286e9::server:8d2fb5bc5ca6eb587de0e5920203309b

So to install Kubernetes on worker nodes I’ll run:

k3s_url="https://k3s-master:6443"
k3s_token="K1037242285167f68f26c05e9221751153591384faab8bb6318c3be56a1ff6286e9::server:8d2fb5bc5ca6eb587de0e5920203309b"
curl -sfL https://get.k3s.io | K3S_URL=${k3s_url} K3S_TOKEN=${k3s_token} sh -

Installation output:

[INFO]  Finding release for channel stable
[INFO]  Using v1.25.6+k3s1 as release
[INFO]  Downloading hash https://github.com/k3s-io/k3s/releases/download/v1.25.6+k3s1/sha256sum-amd64.txt
[INFO]  Downloading binary https://github.com/k3s-io/k3s/releases/download/v1.25.6+k3s1/k3s
[INFO]  Verifying binary download
[INFO]  Installing k3s to /usr/local/bin/k3s
[INFO]  Skipping installation of SELinux RPM
[INFO]  Creating /usr/local/bin/kubectl symlink to k3s
[INFO]  Creating /usr/local/bin/crictl symlink to k3s
[INFO]  Creating /usr/local/bin/ctr symlink to k3s
[INFO]  Creating killall script /usr/local/bin/k3s-killall.sh
[INFO]  Creating uninstall script /usr/local/bin/k3s-uninstall.sh
[INFO]  env: Creating environment file /etc/systemd/system/k3s.service.env
[INFO]  systemd: Creating service file /etc/systemd/system/k3s.service
[INFO]  systemd: Enabling k3s unit
Created symlink /etc/systemd/system/multi-user.target.wants/k3s.service → /etc/systemd/system/k3s.service.
[INFO]  systemd: Starting k3s

Login to one of the master node and check cluster status.

$ sudo kubectl config get-clusters 
NAME
default

$ sudo kubectl cluster-info 
Kubernetes master is running at https://localhost:6443
CoreDNS is running at https://localhost:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

$ sudo kubectl get  nodes
NAME         STATUS   ROLES    AGE     VERSION
k3s-master   Ready    master   14m     v1.24.4+k3s1
k3s-node01   Ready    worker   3m11s   v1.24.4+k3s1
k3s-node02   Ready    worker   3m58s   v1.24.4+k3s1

$ sudo kubectl get namespaces
NAME              STATUS   AGE
default           Active   16m
kube-node-lease   Active   16m
kube-public       Active   16m
kube-system       Active   16m

$ sudo  kubectl get endpoints -n kube-system
NAME       ENDPOINTS                                  AGE
kube-dns   10.42.0.2:53,10.42.0.2:53,10.42.0.2:9153   14m
traefik    10.42.0.5:80,10.42.0.5:443                 14m

$ sudo kubectl get pods -n kube-system
NAME                         READY   STATUS      RESTARTS   AGE
coredns-b7464766c-q9frk      1/1     Running     0          15m
helm-install-traefik-8dhpk   0/1     Completed   0          15m
svclb-traefik-9c2j8          2/2     Running     0          4m49s
svclb-traefik-bf9zd          2/2     Running     0          4m2s
svclb-traefik-v2fpx          2/2     Running     0          14m
traefik-5c79b789c5-k589d     1/1     Running     0          14m

Use crictl command to see running containers.

# Master
$ sudo crictl ps
CONTAINER ID        IMAGE               CREATED             STATE               NAME                ATTEMPT             POD ID
acfafb50852d3       18471c10e6e4b       16 minutes ago      Running             traefik             0                   bf8534452389f
fee5ac7e88f2e       4a065d8dfa588       16 minutes ago      Running             lb-port-443         0                   e7068ff7ab2f2
bbab5b07e5efb       4a065d8dfa588       16 minutes ago      Running             lb-port-80          0                   e7068ff7ab2f2
65c5d1333ea04       2ee68ed074c6e       16 minutes ago      Running             coredns             0                   435c51f4716fc

# Workers
$ sudo crictl ps
CONTAINER ID        IMAGE               CREATED             STATE               NAME                ATTEMPT             POD ID
7ad5c83d6466f       4a065d8dfa588       6 minutes ago       Running             lb-port-443         0                   bf8d9fe57c3f3
c1380eabc0b33       4a065d8dfa588       6 minutes ago       Running             lb-port-80          0                   bf8d9fe57c3f3

Uninstall K3s

The k3s installer script will install k3s and additional utilities, such as kubectl, crictl, k3s-killall.sh, and k3s-uninstall.sh. To uninstall K3s, run the command:

$ k3s-uninstall.sh

Check K3s documentation for advanced configurations.

Other deployment options for Kubernetes available on our site are:

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